<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html;charset=iso-8859-1">
<title>The programs fail?</title>
<style type="text/css"> <!-- @import url(1_.css);   --> </style>
<link disabled rel="stylesheet" type="text/css" href="1_.css">
</head>

<body bgcolor="#ffffff" text="#000000" link="#008000" vlink="#008000" alink="#008000">
<table cellspacing="0" cellpadding="0" border="0">
  <tr>
    <td align="center" valign="middle" width="50">
    <a href="SP_0_Main.htm"><img src="images/abacus.gif" border="0" width="32" height="32" alt="Calc." title="Calc."></a>&nbsp;</td>
    <td align="left" valign="middle"><font size="-1"><a href="SP_0_Main.htm">SED &amp; PREDOM</a>&nbsp;/ <a href="SP_Special_Cases.htm">Special&nbsp;Cases</a></font></td>
  </tr>
</table>

<h3>The programs fail?</h3>

<ul type="square">
<li><b>Singular equilibrium conditions:</b>
  <ul type="disc">
    <li>Check the concentrations for each component.
			Try to change a zero total concentration into a <nobr>log(free activity)</nobr>
      &#8776; <nobr>&#8722;999.</nobr>  This means changing a line saying
			<nobr>&#147;<tt>T,0</tt>&#148;</nobr> to a line saying
      <nobr>&#147;<tt>LA,&#8722;999</tt>&#148;.</nobr>
			This will work with components that can not have negative concentrations (that is,
			it will work for components like <nobr>Ca<sup>2+</sup>,</nobr> but <b>not</b> for
			<nobr>H<sup>+</sup></nobr> or <nobr>e<sup>&#8722;</sup>).</nobr></li>
		<li>Another possibility if a zero total concentration is given:
			try to change it to a small non-zero number, like <nobr><tt>1E-15.</tt></nobr></li>
	 <li>If several total concentrations are the same (for example
			<nobr>[Ca<sup>2+</sup>]<sub>tot</sub></nobr> = <nobr>[Mg<sup>2+</sup>]<sub>tot</sub></nobr> =
			<nobr>[CO<sub>3</sub><sup>2&#8722;</sup>]<sub>tot</sub></nobr> = <nobr>0.001 M),</nobr>
			try to change them slightly (for example, set one component to <nobr>0.001,</nobr> the next
			to <nobr>0.00101,</nobr> the third to <nobr>0.00102,</nobr> etc).</li>
  </ul>
  </li>
<li><b>Impossible chemical systems:</b>
  <ul type="disc">
    <li>Some <nobr>&#147;redox&#148;</nobr> cases (for example an excess free electrons without any left
			material to be reduced) cannot be handled. Try in that case to limit the concentration
			range to reasonable values, see for example the input file <nobr><tt>EX5.DAT</tt></nobr>      </li>
    <li>The programs also fail if the activity for a solid component is given,
			but some other conditions are also given which make the solid component not stable.
			For example:
			 <ul type="circle">
			   <li>In very acid media an oxide or carbonate can not have
													<nobr><i>activity</i> = 1.</nobr></li>
				 <li>A copper(II) compound is not stable under very reducing conditions
												(where Cu metal is stable), do not give its <nobr><i>activity</i> = 1.</nobr></li>
				 <li>Iron metal is not stable under an oxygen atmosphere: do not set
												both the <nobr>O<sub>2</sub>(g)</nobr> and <nobr>Fe(c)</nobr> activities to
												fixed values.</li>
			 </ul>
        </li>
    </ul>
  </li>
<li><b>Input errors</b> should not occur if the input file has been created
  					with <nobr><a href="DB_0_Main.htm">DATABASE</a>.</nobr> Common errors
            if you modify the input file your-self:
  <ul type="disc">
    <li>Check that all components that are specified as solid
							(SOLIDC in the first input line, see <a href="SP_Data_File_Chemical_System.htm">data-file <nobr>format</a>)</nobr>
							indeed do correspond to solid phases. The programs assume that the last SOLIDC
							components are the solid ones.</nobr></li>
		<li><a name="Check_Stoich"></a>
      Look for erroneous equilibrium constants and/or stoichiometric coefficients.
							<b>Check stoichiometric coefficients:</b>  calculate a diagram with SED by setting the
							<a href="SP_Ionic_Strength.htm">ionic strength</a> to a non-zero value
							(for example: <nobr>0.1 M).</nobr> The program will check for electroneutrality
							in all equilibrium reactions and give warning messages for non-balanced reactions.
							This only works if correct electrical charges are given in the
							<a href="SP_Names_Numbers.htm">names</a> of all chemical species.</li>
    </ul>
  </li>
</ul>

</body>
</html>